* minibuffer.el (read-file-name-default): Bind non-essential' to t'.

* net/tramp.el (tramp-file-name-handler): Catch 'non-essential.

* net/ange-ftp.el (ange-ftp-gwp-start, ange-ftp-start-process):
* net/tramp-sh.el (tramp-maybe-open-connection):
Throw if `non-essential' is non-nil.

lisp/ChangeLog

@@ -1,3 +1,13 @@
+2012-06-17  Michael Albinus  <michael.albinus@gmx.de>
+
+	* minibuffer.el (read-file-name-default): Bind `non-essential' to `t'.
+
+	* net/tramp.el (tramp-file-name-handler): Catch 'non-essential.
+
+	* net/ange-ftp.el (ange-ftp-gwp-start, ange-ftp-start-process):
+	* net/tramp-sh.el (tramp-maybe-open-connection):
+	Throw if `non-essential' is non-nil.
+
 2012-06-17  Martin Rudalics  <rudalics@gmx.at>
 
 	* window.el (special-display-p): Signal an error if BUFFER-NAME

lisp/minibuffer.el

@@ -2335,7 +2335,8 @@ See `read-file-name' for the meaning of the arguments."
 	    (if (consp default-filename)
 		(mapcar 'abbreviate-file-name default-filename)
 	      (abbreviate-file-name default-filename))))
-  (let ((insdef (cond
+  (let ((non-essential t)
+	(insdef (cond
                  ((and insert-default-directory (stringp dir))
                   (if initial
                       (cons (minibuffer--double-dollars (concat dir initial))

lisp/net/ange-ftp.el

@@ -1774,6 +1774,10 @@ good, skip, fatal, or unknown."
 
 (defun ange-ftp-gwp-start (host user name args)
   "Login to the gateway machine and fire up an FTP process."
+  ;; If `non-essential' is non-nil, don't reopen a new connection.  It
+  ;; will be catched in Tramp.
+  (when non-essential
+    (throw 'non-essential 'non-essential))
   (let (;; It would be nice to make process-connection-type nil,
 	;; but that doesn't work: ftp never responds.
 	;; Can anyone find a fix for that?
@@ -1905,6 +1909,10 @@ been queued with no result.  CONT will still be called, however."
   "Spawn a new FTP process ready to connect to machine HOST and give it NAME.
 If HOST is only FTP-able through a gateway machine then spawn a shell
 on the gateway machine to do the FTP instead."
+  ;; If `non-essential' is non-nil, don't reopen a new connection.  It
+  ;; will be catched in Tramp.
+  (when non-essential
+    (throw 'non-essential 'non-essential))
   (let* ((use-gateway (ange-ftp-use-gateway-p host))
 	 (use-smart-ftp (and (not ange-ftp-gateway-host)
 			     (ange-ftp-use-smart-gateway-p host)))

lisp/net/tramp-sh.el

@@ -4292,6 +4292,11 @@ connection if a previous connection has died for some reason."
 	    ;; We call `tramp-get-buffer' in order to get a debug
 	    ;; buffer for messages from the beginning.
 	    (tramp-get-buffer vec)
+
+	    ;; If `non-essential' is non-nil, don't reopen a new connection.
+	    (when non-essential
+	      (throw 'non-essential 'non-essential))
+
 	    (tramp-with-progress-reporter
 		vec 3
 		(if (zerop (length (tramp-file-name-user vec)))

lisp/net/tramp.el

@@ -1928,22 +1928,32 @@ Falls back to normal file name handler if no Tramp file name handler exists."
 			(let ((default-directory
 				(tramp-compat-temporary-file-directory)))
 			  (load (cadr sf) 'noerror 'nomessage)))
+		      ;; If `non-essential' is non-nil, Tramp shall
+		      ;; not open a new connection.
 		      ;; If Tramp detects that it shouldn't continue
-		      ;; to work, it throws the `suppress' event.  We
-		      ;; try the default handler then.
+		      ;; to work, it throws the `suppress' event.
 		      ;; This could happen for example, when Tramp
 		      ;; tries to open the same connection twice in a
 		      ;; short time frame.
+		      ;; In both cases, we try the default handler then.
 		      (setq result
-			    (catch 'suppress (apply foreign operation args)))
-		      (if (eq result 'suppress)
-			  (let (tramp-message-show-message)
-			    (tramp-message
-			     v 1 "Suppress received in operation %s"
-			     (append (list operation) args))
-			    (tramp-cleanup v)
-			    (tramp-run-real-handler operation args))
-			result))
+			    (catch 'non-essential
+			      (catch 'suppress
+				(apply foreign operation args))))
+		      (cond
+		       ((eq result 'non-essential)
+			(tramp-message
+			 v 5 "Non-essential received in operation %s"
+			 (append (list operation) args))
+			(tramp-run-real-handler operation args))
+		       ((eq result 'suppress)
+			(let (tramp-message-show-message)
+			  (tramp-message
+			   v 1 "Suppress received in operation %s"
+			   (append (list operation) args))
+			  (tramp-cleanup v)
+			  (tramp-run-real-handler operation args)))
+		       (t result)))
 
 		  ;; Trace that somebody has interrupted the operation.
 		  ((debug quit)